Reconstructing the history of sediment deposition in caves: A case study from Wonderwerk Cave, South Africa

摘要: We applied cosmogenic isotope burial dating, magnetostratigraphy, and grain-size distribution analysis to elucidate the history of sedimentary sequence, composed fine quartz sands silts, Wonderwerk Cave, located on southern edge Kalahari Desert, South Africa. The source for sand is dunes, presently ∼100 km north cave. Field observations suggest a sediment transport scenario that includes eolian sand, abraded size 70–100 µm, Kuruman Hills, temporary storage hill slopes valleys surrounding later deposition inside Our results simple ages sediments from both front back cave range between 2.63 ± 0.17 Ma 1.56 0.10 following initial exposure 310–620 k.y. However, 26 Al/ 10 Be ratios 3.98 0.24 4.08 0.22 measured in sample collected surface outside may imply an signal equivalent 0.78 0.15 Ma, thus reducing possible age buried samples 1.85 0.23 0.18 Ma. paleomagnetic gave polarity sequence N > R N||N, where indicates normal polarity, reverse polarity. This can be correlated with older younger ranges. correlation suggests front, acquisition stable remanent magnetization were not significantly affected by chemical physical processes postburial production isotopes was insignificant. In contrast, at cave, cannot ages, since temporal gap penetration into final have been long (∼10 5 yr), single transition any reverse-normal occurred during Quaternary. highlights need caution when sequences are compared. Cave show similar distributions exposed vicinity Furthermore, calculated preburial concentrations those These similarities environmental conditions rates geomorphic persisted late Pliocene early Pleistocene currently experienced Kalahari, western Ghaap Plain. favor fine-grained